/**
* Returns a variant number between 0 (inclusive) and maxVariant (exclusive). Use this method to
* get the next variant of a question in sequence. For the first attempt it returns a random
* variant and for the repeat attempts it returns next variants in sequence, when the last variant
* is reached it cycles back to the beginning.
*
* @param maxVariant
* @return variant number
*/
public int getNextVariant(int maxVariant) {
// Passing false for the 'incrementSeed' parameter to get the same
// random number generator for all question attempts.
Random r = getRandom(getClass().getName(), false);
if (r instanceof NotSoRandom) {
// If it is an instanceof NotSoRandom that means variant is fixed
// for testing, do not increment the variant
return r.nextInt(maxVariant);
}
return (r.nextInt(maxVariant) + ip.getAttempt() - 1) % maxVariant;
}
/**
* Obtains a random number generator based on the seed, attempts and navigatorVersion passed by
* the test navigator. If 'incrementSeed' is false attempts and navigatorVersion wont be used to
* get the random number generator.
*
* @param sGroup Group name (arbitrary string)
* @param incrementSeed If true, then increments the random seed passed by the test navigator
* @return Random number generator
*/
private Random getRandom(String sGroup, boolean incrementSeed) {
// Returns NotSoRandom object if fixed variant is used.
if (nsr != null) {
return nsr;
}
long randomSeed = ip.getRandomSeed();
// Increment seed if the request is from OpenMark test navigator only
if (ip.getNavigatorVersion() != null && incrementSeed) {
int seedIncrement = MAGIC_RANDOM_SEED_INCREMENT;
if (OmVersion.compareVersions(ip.getNavigatorVersion(), "1.3.0") <= 0) {
seedIncrement = 1;
}
randomSeed = randomSeed + ip.getAttempt() * seedIncrement;
}
long lHash = sGroup.hashCode();
return new Random(randomSeed ^ lHash);
}